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This article concerns the Grey Knights' homeworld; for the Adeptus Mechanicus' massive combat walkers see Titan.

Titan is the largest moon of the gas giant Saturn in the Sol System and is wholly controlled by the Grey Knights Chapter of psychically-active Space Marines who serve as the Chamber Militant of the Inquisition's Ordo Malleus. The fortress-monastery of the Grey Knights is based on Titan, and is carved entirely of basalt. Within the fortress hang pennants, banners and flags commemorating the victories and sacrifices made by the Chapter in their eternal war against the daemons of Chaos, but none other than the Grey Knights would recognise the names of these campaigns. This is because the Chapter operates in oppressive secrecy, beyond the knowledge of the Adeptus Terra and even often of the Imperium of Man's ruling High Lords of Terra. As a part of the Ordo Malleus, the Grey Knights are answerable only to the Inquisitor Lords of that division of the Inquisition and the Emperor of Mankind Himself. Even the location of the Grey Knights' fortress-monastery on Titan is known only to the Ordo Malleus and its agents. Titan itself is surrounded by the rings of Saturn and the other moons of the gas giant which are all highly-secret Inquisition-controlled worlds, including: Mimas, the prison and execution centre of the Ordo Malleus, Enceladus, the home of the most powerful Inquisitor Lords of the Ordo Malleus and other influential Inquisitors of that Ordo, and several other satellite worlds all dedicated to the highly secret Imperial task of confronting the corruption of Chaos across the galaxy.


The Grey Knights Space Marine Chapter is the most mysterious of all the Imperium's myriad organisations. Few outside the upper echelons of the Inquisition hold any knowledge of the Chapter's Founding, and even these most trusted of men and women are denied the full truth. According to legend, the Grey Knights first appeared during the tumult of the Second Founding in the early 31st Millennium after the Horus Heresy when the nine remaining Loyalist Space Marine Legions were first divided into the present-day organisations known as Chapters. Designated Chapter 666, the Grey Knights were the culmination of a project begun by the Emperor during the final days of the Horus Heresy. When the perfidy of his most favoured son, the Primarch Horus, was revealed following the events of the Istvaan III Atrocity, the Emperor foresaw that the end of the Horus Heresy would cost Him greatly, so much so that He would no longer be able to take an active hand in Mankind's survival -- if He survived at all. The very nature of the Horus Heresy had proven that the Space Marines were not immune to the corruption of Chaos as the Emperor had once hoped. So did the Emperor set His hand to plans that would win a wider victory from the ashes of a most personal defeat. Malcador the Sigillite, the Regent of Terra, a man who had served at the right hand of the Emperor for as long as anybody could remember, had been gathering to him men and women with particular talents since the end of the Great Crusade. At first working for him in an informal, secretive and ad hoc capacity, with the enemy at the gates of the Imperial Palace he shared his vision with the Emperor and brought before Him twelve beings of unswerving virtue who he had recruited on his master's behalf.

By the time Malcador returned to his Emperor with these chosen men and women, Terra itself was under siege by Horus' Traitor Legions, and only through the most artful of subterfuge were the Sigillite and his recruits able to pass unscathed through the battlelines and come unharmed and unseen before the Emperor. Malcador initially chose 12 persons of "an inquisitive nature" -- four of those would become the founders of the Inquisition but the other eight, all Space Marines of differing Legions and unparalleled psykers in their own right, would become the eight founding members of the Grey Knights -- the first Grand Masters of the Chapter. In stern silence the Emperor surveyed the robed figures that Malcador had brought before Him, and He saw that his faithful servant had done well. Of the twelve, four were Imperial lords and administrators possessed of inquisitive nature and unyielding strength of mind. The other eight were Space Marines whose abilities were as peerless as their dedication to the Emperor. Some hailed from Legions that had abandoned the Emperor's light in favour of Horus' dark promises, but these Battle-Brothers had never lost their loyalty and had fought the Heresy from within. Fulsome in his approval of the selection, the Emperor bade Malcador proceed with the next stage of his plan.


So dismissed, Malcador and the twelve departed the embattled palace as unremarked as they had arrived. Yet when the group departed Terra they divided, for their destinies would be separate for a time. The four Imperial lords left to lay the framework of the Inquisition -- that mighty and secretive organisation charged with keeping watch over all arms of the Imperium to prevent both corruption within and attack from without -- while Malcador took the eight Space Marines to the moon of Saturn named Titan. Following the dire events of the Horus Heresy, across the galaxy, forces still loyal to the Arch-Traitor continued to fight the war he had declared, razing planets and claiming dominion over vast tranches of human worlds. The forbidden knowledge shown to Horus that had been the catalyst for his fall from grace bore other more sinister fruit, and dwellers from the other side of reality, the Empyrean, were now abroad in the material realm. Though many at the time of the Heresy believed the word to be childish and loaded with superstition, they came to be called daemons, for lack of a better and more descriptive term in the Gothic language. Whatever name given to them, their existence itself was all too horribly apparent. At points all across the galaxy, the Materium had been worn thin and the veil between realities torn open. The Eye of Terror blinked open, casting its malign gaze on the destruction so freshly wrought as world after world became conduits for the unreal to enter the real.

The Loyalist Legions were diminished, their fighting strength a paltry fraction of its pinnacle and their Primarchs dead or at each other's throats in the power vacuum that followed the Emperor's internment in the arcane mechanisms of the Golden Throne. While the Emperor had foreseen the myriad dangers humanity faced and created the Legions in His own image to combat them, even He could not have anticipated the monstrous forces now unleashed upon the Imperium. While the Legions had been bred to fight wars on the material realm, this new foe could battle on the immaterial front too, rendering Space Marines little more effective than the common mortal soldier when it came to psychic war. Many of the Legions had once welcomed psykers into their ranks but an Imperial edict at the Council of Nikaea barring His sons from utilising the potential of their Warp-gifted troops had been passed in the years before Horus's betrayal and endorsed by the Emperor Himself, eliminating the Librarius from every Legion. Denied the one weapon that could reasonably have altered the course of the opening stages of the interstellar civil war, in time the Primarchs came to see its true power and the Loyalist Legions gladly welcomed Librarians among their number once again. But one man had always known the capability of that weapon and had foreseen a time when humanity would need to fight the powers of the Warp with powers born of the Warp.

Through sorcerous means, the Sigilite had long ago occluded the moon of Titan from the sight and deeds of Loyalists and Traitors alike, covertly building a fortress-monastery and equipping it with forbidden technologies and secret training facilities to prepare the new Chapter in its role defending the Imperium from daemonic incursion. New supplies of gene-seed, newly derived from the genetic material of the Emperor Himself, lay preserved in cryovaults, and fresh-forged armaments stood ready in cloistered armouries. Theirs would not be a full Space Marine Legion, but a Chapter -- a smaller, more tightly knit brotherhood, but one with numbers enough for the task at hand. In addition to the eight founders, thousands of others had been taken to the hidden satellite to serve as ancillaries, Chapter Serfs and the recruits that would from the original Brotherhoods (companies) of the Chapter. Malcador oversaw the initial creation of the Grey Knights, but he could not remain to oversee their evolution, so he selected one of the eight to lead the Chapter in the years to come. So did Janus become the first Supreme Grand Master -- the hand that would guide the Grey Knights through their first challenges. Before leaving Titan for the final time, Malcador forged one last enchantment of arcane technology and psychic accumen, greater than any that had come before it. Titan vanished completely from its orbit, hidden from Horus in the most unlikely of refuges -- Malcador had anchored it amongst the tides of the Warp. Protected by Macro-Geller fields and sigilic rites of Malcador's own devising, Titan rode out the tumult of the Warp whilst the rest of the galaxy endured through the last slar months of the Horus Heresy and the tragedy of the Emperor's final battle.

For centuries the Grey Knights dwelt on Titan while the Sigillite kept them hidden from reality, training their minds and arming themselves with the knowledge they would need to go forth and eradicate the daemonic from the material realm. For hundreds of subjective Terran years the Grey Knights trained and prepared, to not only armour their mind from psychic assault but also to turn it into the sharpest blade with which to sever their enemies' links with the corporeal. But knowledge was the most powerful and the greatest of the weapons that they armed themselves with. For hundreds of years the Grey Knights prepared to do battle with the Neverborn, drawing on the entire libraries at their disposal prepared for them by Malcador that were filled with books that listed the rituals of banishment, the rites of warding and, most importantly of all, the true names of hundreds of daemons.

The Return

When the Grey Knights did finally take their place back in the Imperium, less than a standard decade had passed in real time, but for the warriors of Titan many standard centuries had elapsed. Men who were young during the twilight years of the war against Horus were now older than the oldest surviving veterans of the fragmenting Space Marine Legions. Those eight who had previously worn Power Armour of a differing colour had accrued more years than even the most ancient and venerable of Dreadnoughts. Yet, the galaxy was still in turmoil. The surviving Loyalist Primarchs bickered over how best to prevent a rebellion on the scale of Horus’s from ever happening again, while the defeated Traitors preyed upon worlds still loyal to the Golden Throne, as did newly emboldened xenos races. But against this backdrop, the malign influence of the Warp had not dwindled -– if anything, it had intensified –- and the Grey Knights threw themselves straight into the fray. Even at present, in the closing years of the 41st Millennium, the Grey Knights continue their never-ending and secret battle against the Forces of Chaos.

The Citadel of Titan

On Saturn's moon of Titan, nestled in the shadow of Mount Anarch, the fortress-monastery of the Grey Knights, known as the Citadel of Titan, juts from the ice sheets and oceans of liquid methane like a jagged black spire. Long has this fortress stood. Its dusty, echoing halls are hung with battle honours stretching back almost ten thousand standard years, though few outside the Chapter would recognise the names of the conflicts inscribed in the faded gold lettering. This mighty structure, designed to accommodate over a thousand Space Marines and all their weapons of war, stands largely silent and empty. The daemonic threat can strike anywhere across the galaxy and, in opposing that threat, most of the Grey Knights are scattered throughout the stars at any given time. Only in the Chamber of Trials, where the unceasing work of recruitment and training is carried out, does clamour reign. Elsewhere, the Grey Knights go about their duties in silent meditation, their thoughts bent upon their unending mission.

Notable Locations

  • Apex Cronus Bastion - This mighty space station, which is the size of a small moon, orbits Titan and is considered one of the most formidable star fortresses in the Imperium. It is rumoured to surpass even the Imperial Fists Chapter's mighty warship Phalanx in firepower.
  • Archivum Titanis - This is where the battlefield reports of the actions conducted by the Grey Knights are stored within the shelves of the Archivum.
  • Augurium - The silver pinnacle that is the Chapter Augurium lies at the top of the fortress-monastery's tallest tower. Within its mirrored walls, the Grey Knights' Prognosticars go about their rituals and meditations. In function, the Prognosticators are responsible for tracking the unholy spoor of daemons through the roiling tides of the Immaterium to wherever they emerge or are summoned into Imperial space.
  • Broadsword Station - Broadsword Station sits in a geostationary orbit directly above Titan's Grey Knights fortress-monastery. It is a sprawling spiderwork lattice of adamantium and ceramite , bristling with Defence Lasers, Void Shield generators and torpedo batteries. Should the unthinkable happen and Titan come under direct attack, Broadsword Station would constitute the first line of defence. However, its chief purpose is to serve as the orbital dockyard and transport hub for the Grey Knights' fleet of warships.
  • Chamber of Purity - A deep chamber that lies amongst the roots of Mount Anarch, this is the oldest part of the citadel of the Grey Knights. It is here that the Purifiers, the noblest of the Grey Knights, are quartered, and few outsiders are permitted within. The Chapter's legends tell that a great evil lies entombed within, the nature of their prisoner, the Purifiers do not speak of, not even to the Grand Masters of the Chapter.
    • Terminus Decree - The Terminus Decree is a set of ancient instructions written upon millennia-old parchment and sealed within a mysterious artefact of the Grey Knights Space Marine Chapter. This artefact goes unrecorded in all the libraries of the Imperium, for it has been kept secret from all but the Supreme Grand Masters of that Chapter. It is said that the Terminus Decree contains the final secret of the Chapter, a secret so great that it could destroy the foundations of the Imperium -- or provide salvation in its darkest hour. Deep within the Chambers of Purity, within the Grey Knights fortress-monastery on Titan, locked away in the chamber said to hold the tomb of Malcador the Sigillite himself, rests a simple wooden box, embellished with a golden seal. Within this box is the ancient parchment that contains the instructions known only as the Terminus Decree. Only a Supreme Grand Master of the Grey Knights knows how to open the box, and he will do so only when all hope for the future of humanity seems lost. The Terminus Decree is the ultimate sanction of the Grey Knights, a secret so vast it could being the Imperium to its knees, or save it in its darkest hour. The exact nature of the document is unknown, and the only clue to its contents lies in the box's golden seal. It is whispered that it is the exact match of another seal, found only in one place in all the Imperium of Man's many scattered worlds: within the Imperial Palace, upon the Emperor's Golden Throne.
  • Chamber of Trials - It is from the Chamber of Trials that the Gatherers set out across the galaxy in search of new recruits for the Chapter. The Gatherers are Grey Knights whose great age or severe injuries no longer permit them to undertake the primary work of the Chapter, but whose keen senses and minds can still detect an Aspirant hero from amongst the common rabble of humanity. The Chamber of Trials is where Aspirants arrive and their training begins -- if they survive.
  • Cloister of Sorrows - The Cloister of Sorrows was a place of contemplation -- open to Titan's sky, its atmosphere contained within invisible electromagnetic fields so that the great eye of the galaxy could look down upon the Grey Knights. The Emperor was a part of that gaze, always examining the soul of every one of His servants.
  • Dead Fields - Beneath the Grey Knights' fortress proper lies a cool, damp crypt called the Dead Fields. It is here that every Grey Knight wishes to finally reside, in the hallowed halls of the glorious dead. Almost every member of the Chapter will have their body recovered and brought to this crypt beneath the large Temple of the Emperor. As a final tribute to those members of the Chapter that have given their lives in the defence of the Imperium, the names of the dead are carved ceremoniously into a great basalt wall in the heart of the fortress. Among these names are some of the Imperium's greatest heroes, who died in the most horrific circumstances imaginable battling the Forces of Chaos. And like all other matters in regard to the Grey Knights, they will remain almost completely unknown to the rest of the Imperium because of the official policy of denying the existence of Chaos and its daemonic agents to the galaxy at large.
  • Deimos - The moon of Mars called Deimos, known as the Steel Forge, is the Grey Knights' own Forge World, where the manufactoria thunder night and day, providing the Grey Knights with ammunition for Psycannons, armour plating for Land Raiders and heavy ordnance for starships. Many of the Grey Knights' unique weapons and wargear are also produced in Deimos' subterranean halls, though certain items -- chiefly Nemesis Force Weapons -- are carefully crafted by the Chapter's Techmarines in the inviolable heart of their fortress-monastery, whilst others are obtained from the Adeptus Mechanicus -- or other, forbidden sources -- solely under the far-reaching auspices of the Inquisition.
  • Fallen Dagger Hall - The Fallen Dagger Hall is a chamber that serves as a place for close combat training for the Chapter's Neophytes, conducting drills and sometimes as an informal meeting place with Inquisitorial representatives of the Ordo Malleus. This chamber was so-named because Grand Master Kolgano, centuries earlier, challenged the Grey Knights under his command to an unarmoured dagger duel and promised his jewel-encrusted suit of Terminator Armour to anyone who could beat him. Kolgano is long gone, buried unbeaten with his dagger deep in the heart of Titan's catacombs, but the hall remained lofty and echoing.
  • Hall of Champions - The Hall of Champions is the seat of the Paladins -- the Grey Knights' greatest warriors. Rank upon rank of marble statues line the walls, each bearing the likeness of a mighty hero from the Chapter's past; a Paladin, a Brother-Captain or a Grand Master granted graven immortality so that he may inspire the generations of Grey Knights yet to come. In such auspicious company are the Chapter's feast days held, beneath vaulted rafters laden with trophies seized upon the field of battle: weapons, banners, armour fragments and artefacts so unusual as to be unrecognisable. Few of these trophies are daemonic in nature -- rather they are victory tokens captured from mortal foes.
  • Mandulian Chapel - This chapel consisted of a long gallery with a dizzyingly high ceiling, thick with columns and with statues in niches running along the walls. To reach the huge, three-panelled altar at the front of the chapel, a Grey Knight had to walk past the unwavering stone eyes of hundreds of Imperial heroes. Some of them were legends, some had been forgotten, and they represented every part of the web of different civilian and military organisations that kept the galaxy-spanning Imperium together. Closest to the altar was the statue of Grand Master Mandulis himself, who had died a thousand standard years before the late 41st Millennium -- his figure carved into one of the pillars as if he were holding up the chapel's ceiling -- a clear symbolic message that Mandulis, like every Grey Knight, kept the Imperium from collapsing.
  • Sanctum Sanctorum - In many ways, this chamber is the heart of the Grey Knights Chapter, for it contains the accumulated knowledge of their long history, as well as many rare gems of lore garnered from the Emperor's own experiences in the long millennia before that. Herein are recorded the rituals and procedures of the myriad psychic abilities that the Grey Knights call upon, as well as several closely-guarded technological secrets concerning the crafting of Nemesis Force Weapons and some of the other tools unique to the Chapter.
    • Librarium Daemonica - Within the darkest chamber of the Sanctum Sanctorum lies the Librarium Daemonica, the foremost repository of lore on the Warp, sorcery and daemonology in the Imperium of Man. The Librarium is a forbidding place, filled with tens of thousands of tomes, logic stacks and data crystals of diabolic lore the Ordo Malleus has accumulated over the millennia, all maintained by a corps of mnemonic Servitors whose rudimentary minds are routinely wiped to prevent even their basic intelligence from being twisted by the arcane knowledge of the Librarium. The Librarium was placed within the Grey Knights' fortress-monastery because even other Inquisitors fear to be corrupted by the forbidden knowledge kept within; only the Astartes of the Grey Knights have so far proven truly incorruptible by Chaos.
    • Vault of Labyrinths - In one corner of the Sanctum Sanctorum lies a stasis vault, a time-sealed prison from which there can be no escape. Within the vault lie scores upon scores of Tesseract Labyrinths, fist-sized cubes of an alien design recovered from what are now recognised as unawakened Necron Tomb Worlds across the galaxy that are capable of imprisoning beings of pure energy, amongst whose ranks daemons can be counted. Over the millennia, the Grey Knights have succeeded in sealing a few dozen daemons within the extradimensional chambers of Tesseract Labyrinths, thus weakening the daemonic threat by a miniscule degree.
  • Warp Nexus - The Warp Nexus is a star-shaped chamber that lies at the very heart of the Grey Knights' fortress-monastery. The very air within throbs with shackled power. Fuelled by the ceaseless chants and prayers of two hundred Chapter Serfs, it was the mandalas and pentagramic sigils of the Warp Nexus that maintained Titan and the Chapter fortress amongst the turbulent tides of the Immaterium during their time of preparation after the Horus Heresy. In the ten millennia since, much effort has gone into maintaining the Warp Nexus. In part, this is simply because it is one of the few tangible artefacts left behind by Malcador the Sigillite. This is underpinned by the more practical goal of attempting to realign the Warp Nexus' power once again, ensuring Titan has an unassailable refuge in the Empyrean should it be required.


  • Codex: Daemonhunters (4rd Edition)
  • Codex: Grey Knights (5th Edition), pp. 8-9
  • Warhammer 40,000: Dark Millennium (1994), pg. 22
  • White Dwarf 260 (Australian Edition), "Index Astartes - Purge the Unclean"
  • Battle for the Abyss (Novel) by Ben Counter
  • Age of Darkness (Anthology) edited by Christian Dunn, 'The Last Remembrancer' by John French
  • Vengeful Spirit (Novel) by Graham McNeill
  • Grey Knights (Novel) by Ben Counter
  • Hammer of Daemons (Novel) by Ben Counter
  • The Inquisition